In general, the present invention relates to a picture decoding apparatus, a picture decoding method adopted in the apparatus and a recording medium for storing the method. More particularly, the present invention relates to a picture decoding apparatus, a picture decoding method adopted in the apparatus and a recording medium for storing the method whereby a plurality of picture signals are input and decoded at the same time to output decoded picture signals synchronously with each other.
FIG. 1 is a diagram showing a typical configuration of a related art picture decoding apparatus. Data encoded in accordance with an MPEG (Moving Picture Experts Group) system is supplied to a VBV (Video Buffering Verifier) buffer 1 to be stored therein. The VBV buffer 1 is used for absorbing variations in transfer rate for encoded data received at a variable transfer rate before the data is supplied to a variable-length decoder 2 continuously at a fixed transfer rate. The variable-length decoder 2 decodes the encoded data, outputting a picture signal component to an inverse quantizer 3 and a motion vector to a motion compensator/predictor 7.
In the inverse quantizer 3, the input signal is quantized. In an inverse DCT (IDCT) unit 4, a DCT (Discrete Cosine Transform) coefficient received from the inverse quantizer 3 is subjected to an inverse DCT process. The motion compensator/predictor 7 carries out motion compensation on an already decoded picture signal stored in a picture memory 6 in accordance with a motion vector and generates a predicted signal. The output of the IDCT unit 4 is supplied to an adder 5 to be added to the predicted signal output by the motion compensator/predictor 7. A sum obtained as a result of the addition by the adder 5 is stored in the picture memory 6. A picture signal stored in the picture memory 6 is read out from the memory 6 to be output typically to a display unit not shown in the figure.
By the way, in the case of digital satellite broadcasting, picture signals of a plurality of channels (typically, 3 channels) are included in transmission channels for 1 transponder. When pictures of the 3 channels are displayed on a multiscreen as a moving picture at the same time, the decoding system shown in FIG. 1 is required for each of the 3 channels. As a result, there is raised a problem of a higher cost and a larger size.